CORVALLIS, Ore. (AP) Mike Riley, the dean of the Pac-12's coaches embarking on his 14th season at Oregon State, is always unapologetically optimistic each season.

This season is no different - but a big reason behind his hope is returning quarterback Sean Mannion, who decided to stick with the Beavers for a final season.

"There is no doubt about it that Sean has an NFL future. He had a chance to come out early and was going to be drafted relatively high this year, if he wanted to. And I'm glad that he decided to stay with us," Riley said.

Mannion embodies Riley's pro-style offense. The 6-foot-5 senior set a Pac-12 season record last year for yards passing with 4,662 and threw an Oregon State-record 37 touchdown passes, third-most for a single season in conference history.

The fifth-year senior has collected 10,436 career yards passing and could break Matt Barkley's record of 12,274 before the end of the season.

The Beavers started 6-1 last year and Mannion was considered a Heisman hopeful until a five-game losing streak closed out the team's regular season. Oregon State finished 7-6, capping off the year with a 38-23 victory over Boise State in the Hawaii Bowl.

Riley's main concern is who will help protect Mannion: The offensive line lost three starters from last season: Grant Enger, Josh Andrews and Michael Phillip.

Center Isaac Seumalo, who will likely shift positions this season, is still recovering from a broken foot he sustained during the Hawaii Bowl. Fellow lineman Grant Bays has been limited by back issues, and Josh Mitchell was coming off of shoulder surgery.

"For right now, this has to remain a little fluid as we go through camp, just to get a good picture of the best scenario that we can paint by the time we get to the season," Riley said.

REPLACING COOKS: Last season Brandin Cooks won the Biletnikoff Award as the nation's top wide receiver, setting Pac-12 records with 128 catches for 1,730 yards. But now he's with the New Orleans Saints. So who is Oregon State looking to as his replacement? Well, Cooks was a rarity, but the Beavers have Richard Mullaney, who caught 52 passes for 788 yards and three touchdowns as a sophomore last season, and sophomore Victor Bolden, who is looking to have a breakout season, too.

GWACHAM'S SHIFT: After struggling with injuries and inconsistency at wide receiver, senior Obum Gwacham is making the shift to defensive end. He's likely to fall behind Dylan Wynn and others on the depth chart, but at 6-foot-5 and 230 pounds, the former high jumper could have an impact against the pass.

SEUMALO'S STATUS: Like the rest of the offensive line, Seumalo's situation remains "fluid." He's mostly played at center during his career with the Beavers, but Riley suggested he'll move to right guard. The bigger question is when. "We're going to be very, very careful with that. So that's why I'm being very careful when I say he's going to play. But I anticipate him being ready. I would think he might be ready for the first game, but maybe not," Riley said.

RUNNING GAME: Still hoping to bring back the ground game that defined the Rodgers brothers era, the Beavers return Terron Ward and Storm Woods, who combined for 998 yards and 11 touchdowns last year. While Oregon State's running game struggled for much of last season, it showed a spark in the Civil War and the Hawaii Bowl. Riley says he's hoping that trend continues: "(We) Just kept staying with it, and finally got some execution in the last two games that gave us kind of a glimpse into our past. That's how this running game is supposed to look, and also where we have to go in the future," Riley said.

NEW FACE: While Riley's staff is known for its consistency, there is a new face in John Garrett, who takes over as offensive coordinator following Danny Langsdorf's departure. Garrett, whose duties include quarterbacks and tight ends, once played for Riley in the now-defunct World League. He was wide receivers coach for the Tampa Bay Buccaneers last season.

(AP) Southern California has been picked to win its first Pac-12 football title since 2008 in a preseason media poll. The Trojans received 21 of 45 votes for the title, edging defending champion Oregon. More.